I would
appreciate a recommendation! How long should
a CD be replied upon?
You cannot rely on a CD (not even a pressed CD) for
anything important. You need at least two CDs, preferably
more. By the time you realise you were unlucky enough
to hit the bad one in the batch, it is too late.
I've had a few CD-Rs die and two DVD-Rs die. For stuff I
care about, I burn to CD-R twice. I expect to take the
whole lot and reburn to something else eventually. I
keep waiting for the C3D or similar technology to surface
(say 100GB per disc) but I'm still waiting. Given the
drop in ?/GB of had drives lately, I may well put everything
onto a spare drive in the meantime.
If the image file for the CD
is retained, how long before it will not be possible
to burn a new CD and use it on what will then be a
current operating system?
The ISO ormat is well documented. If you ignore various
copy-protections schemes, the for straight-forward normal
CDs, I would be surprised if you cannot access one 100
years from now. You almost certainly won't be able to burn
a new CD-R (since noone wil be making the media) but you
will be able to access an ISO file. If you use something
like Nero with its (I assume ...) undocumented .NRG format,
you'll have to spin up an emulator and a copy of WXP with
Nero. Convert to ISO before then and you should be OK.
I'd be surprised if noone has a working DVD drive 50
years from now. Even the next generation stuff (HD-DVD)
sounds like it will be able to read CDs.
stating when the CD will no longer be readable is
almost
a pure guess, but I was wondering is anyone is willing
to suggest if it will be less than 3 decades or more
than 10 decades?
Surely reading ISO9660 image files will be possible essentially
forever, unless we lose the standard (or the ability to program)!
Being able to read the media may prove difficult beyond 100 years
or so. As long as the current equivalent to CDROM remains based on
rotating media that is read optically, modifying such a drive to
read a CDROM will remain feasible. Once we move to something as
different to CDROM as those are to floppy disk drives, then we
will get to find out how hard it is to build a drive from scratch!
Has anyone built a floppy drive from scratch? Without salvaging
any mechanical parts or heads from an existing floppy? I'm
assuming that electronic processing is not a problem (in
principle) for either floppy disks or CDROMs/DVDROMs.
Jerome Fine replies:
I think I have been asking the wrong question. I suspect
that the best way to handle the problem is by keeping the
ISO image file of the CD on a current media (presently
a hard disk drive of some kind) and using software to
pretend it is the actual CD - normally called emulation,
but not a problem if it is called something else.
I suspect that this is likely to be the most straightforward
solution in the long run - many decades. Almost everyone
seems to expect that neither a CD-R nor a DVD-R (i.e. the
backup media we make for ourselves in single digit numbers)
will last less than 20 years and probably less than 10 years.
I can't think of any media that might be more reliable.
Consequently, since it seems certain that repeated backups
of the original CD image will be needed, why not just use
the original CD image file in the first place.
At present, I am using Windows 98 SE (I realize that this
is badly off topic, but I can't successfully use anything
else with E11 to run my RT-11 programs). Does anyone
have any success with a CD emulation program that will
allow me to use a CD image file (an exact duplicate of
the ISO image file of the CD which was used to burn the
CD in the first place)? Are there both free and commercial
versions? What are the advantages and the disadvantages?
I might as well ask for everything that I might want!
Does anyone have any experience using a CD emulation
program under Windows 98 SE using E11 running any of
the PDP-11 OSs, maybe even RT-11 in particular? If
such an application program is available, this would
allow me to become independent of the actual hardware
other than to use my DVD-R burner to make backups as
often as seems needed, but then direct E11 to use the
CD image file on the hard drive instead of an actual
CD in a CDROM drive.
Sincerely yours,
Jerome Fine
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